Despite initial progress in preclinical models, most known histone deacetylase inhibitors (HDACis) used as a single agent have failed to show clinical benefits in nearly all types of solid tumours. Hence, the efficacy of HDACis in solid tumours remains uncertain. Herein, we developed a hybrid HDAC inhibitor that sensitized solid tumours to HDAC-targeted treatment.

Methods: A hybrid molecule, Roxyl-zhc-84 was designed and synthesized with novel architecture. The pharmacokinetics and toxicity of Roxyl-zhc-84 were analysed. The antitumour effects of Roxyl-zhc-84 on solid tumours were investigated by assessing cell growth, apoptosis and cell cycle in vitro and in three in vivo mouse models and compared to those of corresponding control inhibitors alone or in combination. Gene set enrichment analysis was performed, and relevant JAK1-STAT3-BCL2 signalling was identified in vitro and in vivo in mechanistic studies.

Results: Roxyl-zhc-84 showed excellent pharmacokinetics and low toxicity. The novel hybrid inhibitor Roxyl-zhc-84 induced cell apoptosis and G1-phase arrest in breast cancer and ovarian cancer cell lines. In three mouse models, oral administration of Roxyl-zhc-84 led to significant tumour regression without obvious toxicity. Moreover, Roxyl-zhc-84 dramatically improved the limited response of traditional HDAC inhibitors in solid tumours via overcoming JAK1-STAT3-BCL2-mediated drug resistance. Roxyl-zhc-84 treatment exhibited vastly superior efficacy than the combination of HDAC and JAK1 inhibitors both in vitro and in vivo.

Conclusion: Concurrent inhibition of HDAC and CDK using Roxyl-zhc-84 with additional JAK1 targeting resolved the limited response of traditional HDAC inhibitors in solid tumours via overcoming JAK1-STAT3-BCL2-mediated drug resistance, providing a rational multi-target treatment to sensitize solid tumours to HDACi therapy.

Keywords: HDAC1, CDK4/6, JAK1, inhibitor, solid tumour

尽管临床前模型已取得初步进展，但大多数已知的组蛋白脱乙酰基酶抑制剂（HDACis）作为单一药物仍未能在几乎所有类型的实体瘤中显示出临床益处。因此，HDACis在实体瘤中的疗效仍不确定。本文中，我们开发了一种混合型HDAC抑制剂，可将实体瘤对HDAC靶向治疗敏感。

方法：设计并合成了一种新型的杂合分子Roxyl-zhc-84。分析了Roxyl-zhc-84的药代动力学和毒性。通过在体外和三种体内小鼠模型中评估细胞生长，凋亡和细胞周期，研究了Roxyl-zhc-84对实体瘤的抗肿瘤作用，并将其与单独或组合使用的相应对照抑制剂进行了比较。进行了基因集富集分析，并在机理研究中在体内和体外鉴定了相关的JAK1-STAT3-BCL2信号传导。

结果： Roxyl-zhc-84具有优异的药代动力学和低毒性。新型杂合抑制剂Roxyl-zhc-84可以诱导乳腺癌和卵巢癌细胞系中的细胞凋亡和G1期阻滞。在三种小鼠模型中，口服Roxyl-zhc-84导致明显的肿瘤消退而没有明显的毒性。此外，Roxyl-zhc-84通过克服JAK1-STAT3-BCL2介导的耐药性，大大改善了传统HDAC抑制剂在实体瘤中的有限反应。在体外和体内， Roxyl-zhc-84治疗均比HDAC和JAK1抑制剂的组合具有更优越的疗效。

结论： Roxyl-zhc-84与其他JAK1靶向同时抑制HDAC和CDK通过克服JAK1-STAT3-BCL2介导的耐药性解决了传统HDAC抑制剂在实体瘤中的有限应答，提供了合理的多靶点敏化治疗实体瘤要用HDACi治疗。

关键词：HDAC1，CDK4 / 6，JAK1，抑制剂，实体瘤